Three-dimensional refractive index distribution information of a sample is an important optical feature. For a transparent biological sample, the three-dimensional refractive index distribution information may provide a density and structure information of the biological sample, to give a possibility to image a three-dimensional cell that is not marked.
In an existing bioscience field or medical study, the sample is generally marked with a fluorescence imaging technology. However, once the sample is marked with fluorescence, the property of the sample may be influenced, so as to affect an experimental result. The three-dimensional refractive index imaging is to non-intrusively detect information of a three-dimensional refractive index field of the sample, thereby providing different features of different parts of the sample. Therefore, the three-dimensional refractive index imaging is a hot topic.
Recently, a variety of three-dimensional refractive index microscopic imaging methods are provided. A principle of these methods is mainly to employ coherent lights in different directions to illuminate the sample to obtain phase information in different directions. Therefore, the three-dimensional refractive index information can be computed by using a tomography algorithm. However, these methods have a high requirement on equipment and require complex systems.
Furthermore, during a process of imaging the sample, it is required to shoot the sample for many times. It is hard to obtain the three-dimensional refractive index information of the sample by only shooting the sample once. Therefore, it is a big challenge to capture images quickly.
Therefore, how to quickly and dynamically collect the three-dimensional refractive index information with a high resolution is still difficult to solve.